1. Field of the Invention
The present invention relates to a resonating cavity for ultra-high frequencies, more particularly a resonating cavity used in a generator operating at gigahertz frequencies, for example millimeter and submillimeter waves.
2. Description of the Prior Art
Among the generators of this type, generators in particular are known in which an electron beam is propagated along helical paths while guided by a uniform magnetic field along the axis of the helix. The beam passes through a resonating cavity in which the transverse speed components of the electrons interact with a transverse electric field component of the wave so as to amplify it. The cavities usually used in this type of generator are formed by cylindrical cavities or cavities with two spherical mirrors whose dimensions are calculated for operating in the TE.sub.on mode.
One of the problems often encountered with this type of cavity, particularly when it is desired to operate in a particular high order mode, results from the coexistence of several modes in the cavity, which causes a high probability of oscillations in an undesired mode.